ELECTROLYTIC ANALYSIS OF METALS 2og
weighed alumina is finely powdered and treated with hydrochloric acid
until it appears white, the iron reduced, without filtration, by means of
zinc amalgam, and titrated with permanganate ; the corresponding amount
of ferric oxide is deducted from the total weight of the alumina
2. Determination of the Carbon, Silicon, Manganese, Phosphorus
and Sulphur.—As with iron (see p. 163).
The more usual types of ferro-aluminium contain 10-20% of aluminium.
ELECTROLYTIC ANALYSIS OF METALS
Analysis by the electrolytic method has now reached a high degree o
perfection and forms a valuable aid in the examination of metals and alloys
Owing to their accuracy, their simplicity and their neatness, electrolytic
methods will be given the preference over other methods, and a brief descrip-
tion of the necessary apparatus and a short outline of the conditions to be
observed in the various operations will now be given.
1. Sources of Current.—The continuous current used should not be
very intense but must be as far as possible constant. It may be obtained
from : primary batteries, accumulators, or the street mains.
Primary batteries do not answer very well the requirements of dec-'
trolytic analysis, since they usually yield a feeble current and must there-
fore consist of numerous cells, while they discharge rapidly and are there-
fore costly. The most suitable, owing to the constancy of the current
produced, are : the Daniell cell and its modifications, and the Cupron cell.
Also thermo-electric piles, although very delicate, may be usefully employed.
Accumulators are, however, very satisfactory, as regards both con-
stancy of current and capacity, and they should be used in all plants of good
A.C. Hassium cyanide solution (containing 8 grams